ITER Newsline / 17 July 2017

A note to our readers: Newsline will not be published again until Monday 4 September.

Summer postcards from the ITER worksite

The latest harvest of ITER construction photos may be taken from the same point—the tallest crane on site—but there is always an abundance of new detail to be gleaned. A year ago, the Assembly Building had just been insulated with several layers of cladding and equipped with overhead handling cranes; work on the circular bioshield was newly underway; the cryoplant was still at foundation level; and a large stretch of land now occupied by the twin Magnet Power Conversion buildings was but a barren steppe. Today, in the seventh year of ITER building construction, the platform seems to have no room to spare. Activity has mushroomed in all corners and the pace of progress difficult to keep up with. When we resume publication in September, things will have changed again. And as Newsline has done for more than ten years now, it will continue to cover and document what is happening not only on the ITER site and within the ITER Organization, but also within the global ITER Project and the worldwide fusion community. In the meantime, we hope you will enjoy this selection of summer postcards.

The ring fortress

ITER'ssteel-and-concretebioshield has become the definingfeature of Tokamak Complex construction. Twolevels only remain to be poured (out of six). It is a 'ring fortress," with walls up to three-metres thick, that will completely surround the Tokamak and protect workers and the environment from the radiation generated by the fusion reaction. Over the past year, we've seen the walls rise steadily. Six months ago, part of the first above ground level (L1) could be seen and work was starting onL2. Today L2 forms a complete ring,the first pours are underway for L3, and some rebar elements have already been installedfor top level L4. Now, let's get inside the fortress and see what's happening there ...

The wave factory

A year ago, work was just beginning on the steel reinforcement for the building's foundation slab. The Radio Frequency Heating Building is now nearing the last stages of completion.The space inside the 26-metre-tall buildingwill be shared by two radio-wave-generating systems designed to feed energy, in the form of electromagnetic radiation, into the plasma.

It's all happening inside

Since the giant poster was added to the Assembly Hall's completed exterior in June 2016 the building has lookedfrom afar like a finished project. Butinside, teams have been advancing on finishing works—installingplasterboard,lighting, fire protection,cable trays;jointing andpainting; and creating stairwells and a lift. Most recently, a first coat of varnish was applied to the floor to limit dust,testing of the overhead cranesstarted, and a special zone was prepared forthe building's first and most impressive assembly tools, the twinvacuum vessel sector sub-assembly tools. European contractors successfully achieved an ITER Council milestone in late June by making one part of the Assembly Hall "ready for equipment."

Along skid row

They look like perfectly aligned emergency housing units. But of course they're not: the 18 concrete structures in the ITER cryoplant are massive pads that will each support one 25-tonne helium compressor skid. What appears as 'windows' in the concrete blocks are but passages for the dense interconnecting piping. The concrete blocks are decoupled from the floor in order to prevent vibrations from being transmitted to other systems. Eighteenhelium compressor unitswill be grouped in the liquid helium plant and operated in parallel to provide the necessary gas flow for the liquid helium cooling needs of the Tokamak. The Compressor Building of the cryoplant will also house other helium compressors as well as compressors for the liquid nitrogen plant. The helium compression system of the liquid helium plant involves the use of oil-flooded screw compressors and a large amount of oil. The fact that the compressors are installed at a height of approximately four metres allows the oil to regain the oil separation system through gravity. Oil acts as a lubricant in the compressor system, and also takes away some of the heat from the cycle. Following compression, thehelium (all oil removed) flows to the liquid helium cold boxesin the adjacent building. In general, theheat generated by thecompressors of the liquid helium plant will be evacuated by the flow of a large volume of cooling water—equivalent to 2,500 m3/hour. A part of thethermal energy will be recovered (approximately 12 MW) and used in the heating of other ITER buildings. The Compressor Building occupies more than half of the space (3,400 m²) available in the cryoplant.

The mega converters

They are the most recent additions to the ITER construction landscape. Long and low, the twin Magnet Power Conversion buildings are going up parallel to the ITER cryoplant. According to the ITER schedule, they will be ready for equipment before the end of the year.

Evacuate and dissipate

If ITER were an industrial fusion plant, the better part of the heat generated by the burning plasmas would be used to produce pressurized steam and (by way of turbines and generators) electricity. Only residual heat would need to be dissipated. But as an experimental installation, not designed to produce electricity, ITER will need to evacuate and dissipate all the power the fusion reaction generates. And this means a lot. During the plasma burn phase, the amount of heat to be evacuated from the Tokamak and its auxiliary systems will be in the range of 1100 MW. The complex system of piping, pumps, open and closed loops that form the ITER cooling water system ends up here, in a 6,000 m² area that accommodates cold and hot basins with a total volume of 20,000 m³ as well as an induced-draft cooling tower installation located above the cold basin.


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